The field of electrosurgery includes a number of loosely related surgical techniques which have in common the application of electrical energy to modify the structure or integrity of patient tissue. Electrosurgical procedures usually operate through the application of very high frequency currents to cut or ablate tissue structures, where the operation can be monopolar or bipolar. Monopolar techniques rely on a separate electrode for the return of RF current that is placed away from the surgical site on the body of the patient, and where the surgical device defines only a single electrode pole that provides the surgical effect. Bipolar devices comprise both electrodes for the application of current between their surfaces.
Electrosurgical procedures and techniques are particularly advantageous since they generally reduce patient bleeding and trauma associated with cutting operations. Additionally, electrosurgical ablation procedures, where tissue surfaces and volume may be reshaped, cannot be duplicated through other treatment modalities.
Present electrosurgical techniques used for tissue ablation suffer from an inability to control the depth of necrosis in the tissue being treated. Most electrosurgical devices rely on creation of an electric arc between the treating electrode and the tissue being cut or ablated to cause the desired localized heating. Such arcs, however, often create very high temperatures causing a depth of necrosis greater than 500 μm, frequently greater than 800 μm, and sometimes as great as 1700 μm. The inability to control such depth of necrosis is a significant disadvantage in using electrosurgical techniques for tissue ablation, particularly in arthroscopic, otolaryngological, and spinal procedures.
Radiofrequency (RF) energy is used in a wide range of surgical procedures because it provides efficient tissue resection and coagulation and relatively easy access to the target tissues through a portal or cannula. However, a typical phenomenon associated with the use of RF during these procedures is that the currents used to induce the surgical effect can result in heating of electrically conductive fluid used during the procedure to provide for the ablation and/or to irrigate the treatment site. If the temperature of this fluid were allowed to increase above a threshold temperature value, the heated fluid could result in undesired necrosis or damage to surrounding neuromuscular and/or soft tissue structures.
One attempt to mitigate these damaging effects includes use of a suction lumen on the distal tip of the electrosurgical device to continuously remove the affected fluid from the surgical site and thereby reduce the overall temperature. Typical suction systems utilize a surgical vacuum source that is self-regulated to maintain a pre-set vacuum pressure. Consequently, the pre-set pressure is applied to each and every device regardless of what type of device is being connected. One problem associated with such systems is that the pre-set pressure arising from the vacuum source is not optimized for the specific device and may negatively affect the efficacy of such electrosurgical devices.
U.S. Patent Application Publication No. 2008/0167645 to Woloszko describes a controller that regulates the suction at the site. The controller receives real-time data from the target site and adjusts the flowrate of the suction line based on the data. Though the controller described in the Woloszko Publication addresses suction, it does not determine and control a number of other device specific operational parameters which may affect clinical efficacy.
Another attempt to mitigate the above described damaging effects includes limiting power output. Typically, an electrosurgical generator includes a user interface which allows the user to adjust various power settings, namely, voltage, current, and power. Limiting power output, however, is not always desirable. One power level may be suitable for one type of device and unsuitable for another type of device. Consequently, a pre-set power level without reference to the type of ablation device is not optimal.
An improved generator (The Quantum™ Generator manufactured by ArthroCare Corporation, Austin Tex.) addresses the above described shortcoming. The Quantum Generator is operable to identify the type of ablation device and determine default voltage settings. This provides a fine approach for a number of procedures such as arthroscopic procedures.
However, it is still desirable to determine and control additional operational parameters. Failure to account or control certain operational parameters (e.g., the flowrate of electrically conductive fluid delivered to the target site) can reduce the efficiency of ablation and treatment or lead to undesirable heating of the tissue. In certain open and semi-open procedures such as ENT and spine procedures, a conductive fluid is required to be delivered to the operating field. The conductive fluid is typically provided via a gravity feed or by a separate fluid delivery pump: in either instance the flow rate of the conductive fluid is set manually and often varies from user to user and procedure to procedure. This variability can lead to less than optimal ablation and heating of the tissue.
Accordingly, improved systems and methods are still desired for the electrosurgical ablation and cutting of tissue and in particular, improved systems operable to automatically identify various device specific operational parameters such as flowrate when the ablation device is connected to the generator.